Sigmund Freud (6 May 1856 - 23 September 1939) was an Austrian neurologist who became known as the founding father of psychoanalysis. Freud qualified as a doctor of medicine at the University of Vienna in 1881, and then carried out research into cerebral palsy, aphasia and microscopic neuroanatomy at the Vienna General Hospital. He was appointed a university lecturer in neuropathology in 1885 and became a professor in 1902. In creating psychoanalysis, a clinical method for treating psychopathology through dialogue between a patient and a psychoanalyst, Freud developed therapeutic techniques such as the use of free association (in which patients report their thoughts without reservation and in whichever order they spontaneously occur) and discovered transference (the process in which patients displace onto their analysts feelings derived from their childhood attachments), establishing its central role in the analytic process. Freud's redefinition of sexuality to include its infantile forms led him to formulate the Oedipus complex as the central tenet of psychoanalytical theory. His analysis of his own and his patients' dreams as wish-fulfillments provided him with models for the clinical analysis of symptom formation and the mechanisms of repression as well as for elaboration of his theory of the unconscious as an agency disruptive of conscious states of mind. Freud postulated the existence of libido, an energy with which mental processes and structures are invested and which generates erotic attachments, and a death drive, the source of repetition, hate, aggression and neurotic guilt. In his later work Freud drew on psychoanalytic theory to develop a wide-ranging interpretation and critique of religion and culture.